Stock-based Compensation - Stock-based Compensation Expense Recognized (Detail) - USD ($) |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
| Total Stock based compensation | $ 118,324 | $ 172,018 |
| Research and Development [Member] | ||
| Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
| Total Stock based compensation | 8,856 | 6,614 |
| General and Administrative [Member] | ||
| Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
| Total Stock based compensation | $ 109,468 | $ 165,404 |